RHCA Study notes: RH442-UNIT9 kernel timing and process delay

Unit 9 Kernel Timing and Process Latency kernel timing and process delay Learning Goals:A. Understanding how the CPU tracks the time B. Adjust the number of CPU accesses c. Adjust schedule delay D. CPU task tuning on virtual machines 9.1 How Linux tracks time Linux under the time trackingA. A hardware timer is timed by using a clock. Includes the following time resources: A. Real Time Clock (RTC): The realtime clock is the device used to keep the system time in place, even when the system is turned off, and it can be timed by the power of the micro-battery provided on the motherboard. B. Time Stamp counter (TSC): Timestamp counter C. Advanced Programmable Interrupt Controllers (APIC) programmable Interrupt Controller D. Programmable Interrupt counter (PIC) programmable interrupt counter B. All events on the system are controlled by the number of Beats (Ticks). The total number of Beats generated after the system startup is recorded through the kernel variable jiffy. B. Pic generation time Interrupt Frequency (hz/sec): Standard: 1000Hz (1 beats =1ms) kernel-xen:250hz (1 beats =4ms) view real time clock: cat/proc/ Driver/rtc 9.2 Tuning System Ticks system beat number adjustmentA. Adjust the tick_divider=value in the kernel boot parameter to use the following values: 2=500 Hz 4=250 Hz 5=200 Hz 8=125 Hz 10= is limited to X86 and x86_64 architectures and does not support Xen. B Conclusion Adjust the system beat number can: A. Reduce CPU load B. This scheduling is unfair to interactive processes. 9.3 Tuning Processor speed Adjust processor speedA. The system will automatically adjust the CPU speed a. Do not use CPU clock cycles to improve efficiency B. CPU speed can be reduced without compromising performance C. The default value, B, is set by the/etc/init.d/cpuspeed file at system startup. Configuration Guide configuration file:/etc/init.d/cpuspeed parameter: Max_speed min_speedc. Conclusion A. Power consumption can be reduced without changing the IO range. B. Adjusting the CPU clock frequency can interfere with the time record. 9.4 IRQ Balancing Load BalancingA. A hard interrupt will preempt the current process a. Interrupts generate delay B. View the IRQ ProcInfo CAT/PROC/INTERRUPTSC. IRQ Load Balancing

RHCA Learning Note: RH442-UNIT9 kernel timing and process delay